A technique for the high-speed characterization of ultrasonic transducer insertion loss performance

A characterization technique has been developed to address the problems associated with calibrating very-high frequency (i.e., > 50 MHz) ultrasound transducers. The technique is based on using a pc-controlled network analyzer to acquire the through-transmission voltage transfer function spectrum from a pair of ultrasound transducers which are closely spaced in water. This spectrum, which includes electrical feed-through noise and multiple reflection artifacts, is then corrected for the water's attenuation and the transfer response of the electronics system. An inverse Fourier transform is then performed, to produce the time domain response of the transducers. The portion of the response which corresponds to the first acoustic arrival is then gated out of this response, and a Fourier transform is performed to compute the transducers' true transfer function (insertion loss) spectrum. A pc-controlled automated calibration system based on this technique has been developed and numerous transducer pairs have been tested. Excellent agreement has been shown between this method and the conventional tone-burst technique for accurately characterizing insertion loss spectra. In this paper, a detailed description of the technique, actual transducer test results, and comparisons with the conventional tone-burst method are presented in detail.